Severe OTA Interference From New Digital Services Tower - Page 10 - Canadian TV, Computing and Home Theatre Forums

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post #136 of 149 (permalink) Old 2013-10-08, 03:20 AM
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Specs for 4G/LTE Filter from Radio shack website:
http://www.radioshack.com/product/in...rName=Category

Insertion loss 1dB between 50-600MHz
Insertion loss 3.5dB between 601-698MHz
Return loss 12dB between 5-698MHz
Rejection 50dB between 740-1000MHz

NOTE: NO SPECS FOR FILTER ROLL-OFF CHARACTERISTICS IN THE CRITICAL 698-740 MHz REGION!!!!!

Note the 3.5 dB Insertion Loss for Ch36-51, which can seriously degrade sensitivity on HALF the UHF Band.
Unless you KNOW there is a 4G/LTE Tower within a few miles of your location, you probably DON'T need it.

I addressed effectiveness of various Low Pass Filters against LTE's 700 MHz Band here:
http://www.digitalhome.ca/forum/show....php?p=1388395
Radio Shack may be the least expensive, but it isn't very effective if an ATT 4G/LTE is close and you need a TRULY effective filter. Verizon 4G/LTE is in a higher band and hence is not as much of a problem. Fol. includes info on how to determine if you are close to a 4G/LTE Tower (there may be other, better methods):
http://www.digitalhome.ca/forum/show....php?p=1693522.
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post #137 of 149 (permalink) Old 2013-10-08, 10:58 AM
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If you don't need to receive channels 49-51, a Soontai LPF-680 might be a good option. They haven't published specs for this particular model, but they do have specs for the LPF480. Assuming the specs can be correlated (and yes I know you should never assume), I would expect it to have more than 20dB attenuation above 700MHz and close to 50dB above 716MHz. As for the pass band, I would guess it will have less than 0.5dB loss under 600MHz, less 1dB loss up to 650MHz and less than 3dB loss up to 680MHz (educated guesses). One would have to see the actual specs for the LPF-680 to be sure however.

The big question is where can we buy this filter and how much will it cost?

Link to my TVFool results is in my profile Homepage URL. I suggest others do the same.

Last edited by roger1818; 2013-10-08 at 11:09 AM. Reason: Added link to specifications.
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post #138 of 149 (permalink) Old 2014-04-17, 01:14 PM
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Rogers rolls out 700MHz in some areas

According to this thread, Rogers has begun rolling out 700MHz coverage in select areas. It would be interesting to see if anyone has noticed recent interference as a result?

DMX 68' tower, HyGain HAM 5 rotator, Antennas Direct DB8e & C5, Channel Master 7777 preamp, Siemens surge protection
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post #139 of 149 (permalink) Old 2014-04-17, 01:33 PM
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Time to point my ol' TV antenna - UHF corner reflector yagi, top of tower, at the nearby 700 Mhz LTE tower and start pumping some 700 Mhz noisy power up the tower - haa haa - just kidding of course.
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post #140 of 149 (permalink) Old 2014-04-21, 10:57 PM
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Quote:
Originally Posted by roger1818 View Post
If you don't need to receive channels 49-51, a Soontai LPF-680 might be a good option. They haven't published specs for this particular model, but they do have specs for the LPF480. Assuming the specs can be correlated (and yes I know you should never assume), I would expect it to have more than 20dB attenuation above 700MHz and close to 50dB above 716MHz. As for the pass band, I would guess it will have less than 0.5dB loss under 600MHz, less 1dB loss up to 650MHz and less than 3dB loss up to 680MHz (educated guesses). One would have to see the actual specs for the LPF-680 to be sure however.

The big question is where can we buy this filter and how much will it cost?
I was curious, so I asked how much it would cost for a small order (10-20 units). They said:

Quote:
such small q’ty samples have to be HAND MADE by our engineers so you must understand the engineering sample cost would be much higher than normal mass production parts. If you’d order at least 100pcs which is our MOQ for mass production line I can provide better offer to you.
and the unit price in the quote was US$299.00. :O

Out of curiosity, I asked how much it would cost for 100, and the unit price plummeted to US$5. Yes, you can order 100 for less than the cost of 2. Welcome to low cost region manufacturing. Both of these prices are FOB from Taiwan and there is a 5% handling fee for credit cards.

Link to my TVFool results is in my profile Homepage URL. I suggest others do the same.
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post #141 of 149 (permalink) Old 2015-08-22, 11:40 AM
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Channel Vision 3102-104 Specs indicate it PASSES up THRU CATV Ch102 (660-666 MHz) and has a 4-channel wide Slope to the High Attenuation Region, which would start at about 666+24 = 690 MHz, which means it should be just what is needed for suppressing 4G LTE Cell Tower signals, unfortunately they don't indicate HOW MUCH ATTENUATION is provided (BOO, HISS)....but even 15-20 dB should be more than adequate:
Low Pass Filter Blocks Channels Above 105 ? 3102-105 | Channel Vision Technology
Low Pass Filter Blocks Channels Above 105

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post #142 of 149 (permalink) Old 2015-08-22, 12:00 PM
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I have the Radio Shack 1500396 LTE low Pass Filter that Adtech characterised a while ago.
Left my Phone up top on the chimney doing some data sessions one day,
and ran 905Shmick's hdhomerun script to measure signal strength and quality on all received stations without it.
Then I put the filter inline between antenna and preamp, and did the same thing. I saw no noticeable difference in SNR at the time.
Thus I removed it from the system as it didn't seem necessary for me.

maybe I'll try that exercise again someday and post results here (we have an RF 49 here).

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post #143 of 149 (permalink) Old 2015-08-23, 04:11 PM
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Did you ever find a dealer for the Soontai filters? Back around 2008, when they didn't list any off-the-shelf values, they said they would build me any roll-off hi-pass filters for $2.00 each or low-pass filters for $1.25 each (or the pricing might have been vice-versa, I forget) as long as I ordered a minimum of 500 of each value. At the time, I could have digested a lot of various values to match my market situation, but I never was able to get any other dealers to take a big enough share to make it worth my while, and I have less need for them now as I did at that time.

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post #144 of 149 (permalink) Old 2015-08-24, 10:24 AM
 
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Has anyone contacted Industry Canada re the interference? Is this going to be the norm?
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post #145 of 149 (permalink) Old 2015-08-24, 12:52 PM
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Found it...ADTech's Measurements on Radio Shack 1500396 LTE low Pass Filter. Has 1.6 dB Insertion Loss on 620 MHz (Ch38/39) and 4.4 dB on 698 MHz (Ch51), which is a bit more than desired.

But it is VERY Effective (40+ dB) against AT&T Cell Tower Transmissions on 734-746 MHz....and low to moderately effective against YOUR AT&T Cell Phone, operating VERY CLOSE to the Antenna (and Tuner) on 704-716 MHz...but at least you can SEE when you cause EMI and MIGHT be able to take actions to minimize the impact on TV viewers: [Verizon uses next higher Band of Frequencies, so is much less of a problem.]


Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2015-08-24 at 01:12 PM.
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post #146 of 149 (permalink) Old 2015-08-26, 03:11 AM
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PS: Band Ownership may vary with location, esp in Canada, where Bell and Rogers use same lower 700 MHz band assignments as AT&T in USA:
https://en.wikipedia.org/wiki/List_of_LTE_networks
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post #147 of 149 (permalink) Old 2015-08-26, 11:23 AM
 
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It also varies here in the US. My Verizon 4G service DL band is in the 734-746 block here in St Louis. Shows up really prominently on any noise figure testing I do of non-shielded amplifiers since VZ has a tower less than 1/2 mile from here.

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post #148 of 149 (permalink) Old 2016-09-23, 02:31 PM
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Charles Rhodes (TV Technology Magazine) measured Frequency Response of CM Stand-Alone LTE Filter. It provides about 50+ dB Insertion Loss against ATT+Verizon Cell Towers [734-758 MHz]....but there is significant LOSS on Upper UHF Frequencies....so Do NOT use one unless you NEED IT:
Out-of-Band Interference: Myth or Reality? | TvTechnology

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #149 of 149 (permalink) Old 2017-05-14, 01:58 PM
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4G and OTA

Is anyone having interference with OTA reception from nearby 4G cell towers
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